When I graduated in 1975 I owed $10,000 in student loans. Repayment was deferred until I finished graduate school, and then I started making payments that lasted 10 years. It's the best investment I ever made.
There is neither a single nor a simple reason for the exploding cost of college. Quality higher education has always been relatively expensive. In fact, it is often more costly to deliver than what is paid by tuition.